Carburetor of combustion engines with automatic fuel regulation



March 16, 1954 w. ZARNACK 2,672,329 CARBURETOR OF COMBUSTION ENGINESWITH AUTOMATIC FUEL REGULATION Filed July 6, 1950 INVENTOR.

WERNER ZARA 145K L Z/W AFFORNEJ Patented Mar. 16, 1954 OMBUSTION ENGINESWITH AUTOMATIC FUEL REGULATIUN Werner Zarnack, Lockstedter Lager-Nord,Germany Application July 6, 1950, Serial No. 172,249

Claims priority, application Switzerland July 13, 1949 CARBURETOR OF C 3Claims.

Carburetors are used for the regulation and formation of the combustiblemixture in socalled Otto-engines in which the proportion of mixture ofair and fuel is determined thereby that the effective pressure producedin an air nozzle, air funnel or the like is transmitted to a calibratedfuel nozzle in such a way that the two effective pressures are equal andtherewith the proportion of mixture equals to the proportion of thecross-section of the air and fuel nozzle. If the mentioned twocross-sections remain constant also a substantially constant proportionof mixture would result independent of the load of the engine and of thenumber of revolutions. This supposition essentially also prevails if, asin the so-called foam nozzle carburetors, additional or correcting airis added to the fuel before its exit into the air funnel where in themost cases the mixing of air and fuel happens, provided that thedimensioning of the spraying tubes and the forming of the nozzlescorrectly considers the rules of the mechanics of flow. Thenapproximately the following conditions exist:

Herein means:

Gr=weight of the air sucked in per time unit,

Gse=weight of the fuel sucked in per time unit,

jz.=narrowest cross-section of the air funnel,

fa==narrowest cross-section of the fuel nozzle,

yz.=specific gravity of the air sucked in,

'yse=specific gravity of the fuel.

In connection with carburetor of vehicles the variability of '11. may beneglected, While the variability of 'yi. requires special regulatingdevices in connection with carburetors of aeroplanes.

For the purpose to balance alterations of the load of the engine mostlya throttle valve or a sliding valve is provided behind the place wherethe combustible mixture is formed; or, if the throttle valve is arrangedin the direction of the air flow before the air funnel, mechanicaldevices are known regulating the feeding of the fuel according to anempirically found law or said devices act in a similar way as the depthrudder of carburetors of aeroplanes.

For small engines, especially engines of motor cycles, carburetors areusual in which the place where the combustible mixture is formedcoincides with the throttling place. The controlling of such carburetorsis made fully empirically by considering the variable air cross-sectionon the mixture forming place by simultaneously changing thecross-section of the fuel nozzle. In consequence, however, of the verysmall fuel crosssections the desired regularity cannot be reached. Thedescribed methods of regulating and forming the combustible mixture havegreat disadvantages.

If the carburetors are provided with a constant air measuring and fuelmeasuring crosssection a quadratic decrease of the effective pressureresults from a decreasing load, so that the suction effect of thecarburetor and therewith the atomizing of the fuel rapidly decreases. By

this regularity for example also the arrange-r ment of a device forrunning without load became necessary, ending on the edge of thethrottling valve and constituting a second mixing place of air and fuel.Thereby the fuel supply depends upon the depression on that mixing placefollowing very complicated rules. Thus it happens that the simplerelation between the quantity of fuel and air is very considerablydisturbed by the added device for running without load. The regulationof fuel and air will therefore not have approximately equal results forall loads but essentially depends also upon the position of thethrottling valve. Further especially within the region of transitionfrom running without load to running with artial load very undesireddiscontinuities of the proportion of mixture result.

A further considerable disadvantage of these mostly used carburetorsarises during the forming of the combustible mixture. The formin of thecombustible mixture should suitably take place on the place of thegreatest air speed because there the mixture is the most intimate andperfect. Instead of that, here the mixture is again deposited in thesecarburetors behind the place of forming the mixture, the throttlingvalve being partially closed, and the mixture must be formed anew whenpassing through the throttling place. As further in consequence of thedifferent circumstances of flow the passage through the throttling valveis quite different on the two halves related to the axis also themixture behind'the throttle valve is very differently concentrated. Themixture is stripped.

The quality of the atomizing further depends upon the rate of decreasein pressure on the nozzle at a given cross-section. Now, as the rate ofdecrease in pressure becomes smaller in the square of the load also forthis reason the fuel preparing on the exit of the nozzle becomes bad ifthere is a partial load.

These circumstances are an essential reason for the bad consumption ofpartially loaded engines working with the usual carburetors. In thisrespect the conditions on the usual carburetors of motor cycles are morefavorable as here the forming of the combustible mixture takes place infact on the place of the greater speed of flow.

There is however the difficulty to correctly dimension the jet needledestined to change the cross-section of the fuel nozzle proportionallyto the alteration of the cross-section on the mixture forming place. Inconsequence of the high speed of flow at the throttling place thecoefficients of flow resulting in a deviation from the quadratic rule offlowing are of considerable importance so that it is impossible to shapethe jet needle so much approximate that the desired constant proportionof mixture or the required dependency of the proportion of mixture onthe air quantity results with every load.

Further it is clear that the air slide which mostly is cylindricallyshaped in combination with the air suction pipe socket of the carburetorar-' ranged rectangularly thereto on the narrowest place does not form across-section formation adapted to be inserted into the equation of flowas measuring cross-section fr, so that the effective pressure happeningon the fuel nozzle is not at all a measure for the flowing air volume.The proportion of mixture, therefore, is very fluctuating with the loadand the number of rotations even if the jet needle is accurately shaped.Also in that case a high consumption results with par tial load.

The improved device according to the invention removes the abovedescribed disadvantages of the mentioned two systems. of carburetors bythe fact that the, forming of the mixture takes place at the place ofthe highest speed of flow, i..e. on the throttling place, itself.Further ac-.- cording, to the invention is automatically made by asimple controller in dependenc on t r fl ct pres ur m asured in an a rfu nel havi n. h ari ab e cr ect on.

The al m suri P 3? ma be ar an e n. that a a e qr th thro t in la f heir. a actwh h is o b nre rrc n ons qu nc of the so reached greatermeasuring exactness, or:

behind he h ottl n p ac in a ficien t n e. if the variable air densityis correspondingly considered. In the improved carburetor theconstruction of the thr ttl n p a s of n nflu nc at all to themeasuring. exactness, of the device as the fuel measuring nozzle is,arranged between the float chamber and the controller in such a way thatit remains free of all. disturbance .fac-.

tors of the air flow. It is further without any importance whether thereare arranged for example twisting devices behind the controller, in theflow-- ing direction of the fuel for the purpose for ameliorating theatomizing. The proportion of mixture is determined in every case only bythe cross-section of themain nozzle and. the crosssection of the airfunnel. This assumption naturally is only correct if the decrease ofpressure on the throttling valve is sufficiently high to overthe meterinof the fuel come the flowing resistances of the mixture of fuel andatomizer air between the regulating valve and the spraying nozzle.

As with decreasing load until a smallest partial load (10-20% of thefull load) the action of the regulator intermits in consequence of thequadratically decreasing effective pressure a no-load device of theusual form is necessary. But also this device does not influence theproportion of mixture if the regulator starts with increasing partialload as the quantity of fuel escaping from the slow running jet is alsomeasured by the main nozzle and the regulator only allows so much fuelto pass as required on both nozzles altogether.

So it is also possible to arrange only one regulator and one mainmeasuring nozzle in multicylinder motors and to provide any number ofthrottling places. or mixture forming places on different places of thesuction tube. In this case only one air measuring place may be providedor the measuring tube lines of a plurality of air measuring places maybe conducted to one sole regulator.

The new regulator becomes very simple especially by the fact that theeffective pressures A101. and AZJBe are divided. The negative pres ysures are conducted to the two sides of amenifully opened the narrowestcross section of the; carburetor must be of such size that the decreaseof pressure from the air funnel until the throttling place is greaterthan the loss of pressure of. the fuel from the place behind the fuelmeasuring nozzle until the exit of the spraying nozzle. including theexit losses.

The drawing shows by way of example two embodiments of the, invention,Fig. 1 being a diagrammatioal illustration of theone and Fig. 2. of. theother embodiment.

According to Fig. 1 the air enters through the air suction pipe socket land flows through the air funnel 2 to the throttling and mixture formingplace 3. throttling valve or. throttling slide 8 of any desirableconstruction is provided. The valve or slide is operated by any suitableleverage not shown and described.

The fuel is delivered from the fuel container not shown in the drawingthrough the opening 5 and over the throttling needle 1 into the floatchamber 8 ofknown construction, and from there to the main fuel nozzle 8and over the throttling needle 9 of the regulator to the spraying nozzleH. When partially loaded with a small loador when idly running theregulator closes automatically, in a ivenc se n e he ect onof the. smalrclditional spring. 12, said spring beingsimultaneously. a valuablemeansfor influencing the characteristic; of the regulator. In thisieventthefuelescapes through the slow running jet l3 which if desired, may becontrolled by aneedle IA. The atomizing in: the sprayingpipe. maybeeffectively.

ameliorated by additional airentering through the, nozzle R5, or bytwisting deviceson the exitof; the fuelwithout the re u at on. einfiuencedthereby.

take pipe. This velocity difference is brought:

For limiting the output or power a Downstream of the intersection of thepipe I!v with the funnel 2, the latter still further converges or isreduced, in order to yield a further pressure drop at the point of fuelejection by the nozzle ll even when the throttle 4 is fully opened. Thepressure drop must be large enough so that air 7 may also be taken inthrough the auxiliary air nozzle l5.

The negative pressure on the fuel nozzle is conducted through the pipeline i into the chamber l8 and the negative pressure on the air nozzlethrough the pipe line H into the chamber l 9, the two chambers beingseparated from each other by a membrane. The positive pressures areshort circuited by the pipe lin to. The regulator operates as follows:

During idling, the throttle 4, as best shown in Fig. 1, is closed sothat only a small amount of air will pass through the funnel 2. Duringthis idling the pressure drop between the points of intersection withthe socket and funnel with the pipes and I! is correspondingly small.For this.

reason, the spring l2 will be made sufl'iciently strong to close thethrottling needle 9 of the regulator. The fuel needed for idling isbeing calibrated accordingly by the nozzle 53 and, where thereisprovided a regulation for said nozzle S3, for instance the needle 14,the calibration is also aided thereby. Where there is provided no needleM, the idling fuel feed will be regulated by the size of the nozzle l3and the size of the auxiliary air nozzle 15.

When the throttle 4 is opened wider and therefore the flow of airthrough the funnel 2 is increased, the regulator will be opened. Thethrottling needle 9 of the regulator will admit an amount of fuelnecessary to cover the fuel required in addition to that fed through thenozzle l3, for ejection through the nozzle l l. The calibration of theamount of that fuel is made by the nozzle 8. Thereby the quantity offuel increases until the pressure behind the fuel nozzle 8 is exactly asgreat as the pressure in the air funnel 2 so that the regulator is againbalanced.

Another embodiment of invention in which a plurality of mixture formingplaces are combined with one sole regulator is shown in Fig. 2. In thisfigure 2| designates the float chamber and 22 the fuel regulatorconnected with the negative pressure of the fuel nozzle 24 by the pipeline 23, while the negative pressure of the air measuring nozzle 25 isconnected with the regulator by the connecting pipe 26 and theassembling pipe line 21. In the pipe line 21 therefore the averagepressure of the measurements in the air funnels 25 prevails so that alsoan average pressure is adjusted on the common fuel measuring nozzle. Bythe pipe line 28 the positive pressure of the air measuring nozzle 25 isconnected with the float chamber. Exactly as described with respect tothe negative pressures of the air measuring nozzles also here the twopressures may be combined to an average value. In the pipeline of thefuel also the common atomizing nozzle 29 is provided. The fuel flowsthrough the admitting socket 30 into the float chamber 2| and over themain measuring nozzle 24 to the regulator 22. After passing theregulating valve the fuel flows into the assembling pipe 3| and fromthere to the spraying nozzles of which any desirable number may be'especially simple by using only one regulator and only on float chamber.

Having thus particularly described the nature of my invention and themanner in which the same is to be performed what I wish to have coveredby Letters Patent is:

1. In a carburetor, for use in connection with a combustion engine, incombination, an air pipe having a wide section, a converging sectionadjacent thereto abruptly narrowing the width of said pipe as comparedto said wide section, a narrow section spaced from said convergingsection and constituting the smallest width throughout said pipe, and afunnel section extending between said converging and narrow sections andcontinuously converging between the widths thereof, whereby air flowingthrough said pipe from said wide section to said narrow section willundergo a first pressure drop between said wide and said convergingsections and will undergo a second pressure drop between said convergingand said narrow sections, throttle means disposed in said narrow sectionand operable for reducing th Width thereof, a fuel conduit comprising afloat chamber structure including a regulatable inlet pipe, meansoperable in response to the amount of fuel prevailing at any moment insaid chamber for regulating the amount of fluid delivered by said inletpipe and comprising a valve, a float for opening and closing said valve,and an interconnection be-- tween said wide section of said air pipe andthe upper portion of said chamber structure, a fuel pipe connected tothe lower portion of said chamber structure and interconnected to saidnarrow section of said air pipe and operable for delivering controlledamounts of fuel sidewise thereto, and means connected to said fuel pipefor controlling the amount of fuel passing therethrough comprising avalve and a regulator interconnected to said converging section andbeing operable to actuate said valve in response to predetermined valuesof differentials between the pressure of the fuel flowing in said fuelpipe and the pressure prevailing in said converging section.

2. In a carburetor, for use in connection with a combustion engine, incombination, an air pipe having a wide section, a converging sectionadjacent thereto abruptly narrowing the width of said pipe as comparedto said wide section, a narrow section spaced from said convergingsection and constituting the smallest width throughout said pipe, and afunnel section extending between said converging and narrow sections andcontinuously converging between the widths thereof, whereby air flowingthrough said pipe from said wide section to said narrow section willundergo a first pressure drop between said wide and said convergingsections and will undergo a second pressure drop between said convergingand said narrow sections, throttle means disposed in said narrow sectionand operable for reducing the width thereof, a fuel conduit comprising afloat chamber structure including an inlet pipe and a float having avalve needle, said float floating in the fuel within said structure andbeing operable for closattests ii'i with said needle said inlet when thelevel of said fuel sure a predetermined height inside of the strutstore, an air chamber formed in said structure above the level of thefluid thereof and intereemznunieatmg with said wide section of saidairpipe, a fuel pipe eonneeted to the underside of said sweaters andoperable for oiive' iih' said tile} and ifielii'diiie a first fiielnozzle, a second file! riezzieadjacent said narrow seetioii of "said airneeded beiifg des rable for delivering sidewise fuel into said narrowsection; and a valve inter= iiidiatesaid ii'oiz'le's operable forinterrupting the between said rioi'zls, means actuable new f tiel foroperating said valve in'response to said pres-- sure drops comprising aho sing, a diaphragm ea titiohi-iig said housing into two compartmentsin driving eeaneetms said valve; partmeilt nearest said valve beansinter tifa'iletdto said reei pipe to ieeive real that said first timeand the other compartfi fifit acing with said eenveeging" seii'tioilpine, an air intake nozzle adi liit said 'soflii nozzle;

3: a earburetor {of use in connection With a cifiib'ustioii engine inoorflbi'l'iation, an air leaving it Wi'ti seetren it eenv'ersing sectionad jaeent thereto abruptly narrowing the width of said pipe as temperedto said wide section, a naarow spaced from said converging seeden andconstituting the smallest width throughout said lpipe, and a funnelsection ex-tendingbe= tween said converging and narrow sections andcontinuously converging between the widths thereoftwhereby air flowingthrough said pipe rrem said Wide Section to said narrow section willundergo a first pressure drop between said wide and said convergingsections and will undergo a second pressure drop between said convergingand said narrow sections, throttle means disposed in said narrow sectionand operable for reducing the width thereof, a fuel conduit comprising afloateh'amber structure mcluding an inlet pipe and being this i3 3? anda floatliaving a valve needle, said float float ingin the fuel withinsaid structure and. being operable for closing with said needle saidinlet when the level or said :uel surpasses a predetermined heightinside of the structure, an air chamber formed in said structure abovethe level of he ruel thereof and intercommunicatins with said Widesection of- Said air pipe, a fuel pipe eonnested to the underside ofsaid structure and op stable for conveying said fuel and indiudirig afirst fuel nozzle, a second fuel nozzle adjacent said narrow section ofsaid air pipe and being operable for delivering sidewi'se fuel into saidnarrow sec tion, and a valve intermediate said nozzles openable forinterrupting the new of fuel between said ne'zzles, means actuable foroperating said valve in response to said pressure drops comprising ahousing, a diaphragm partitioning said housing into two compartments andbeing in driving'cenn'ztiori with saidvalv'e, the Compartment nearestsaid Via-I've being} interoonnected to said fuel pipe to receive fuelthat passed said first nozzle and the other eem' artmentinteroommunicatifig with said conver in section of said air pipe, and are;- uiatabl third fuel nozzle connected to said fuel pipe and operableto receive ruel from said first nozzle and intereommuineating with saidnarrow section of said air pipe for delivering 'sidewise a resold-tableamount of fuel thereto, and an air intake nozzle adjacent said secondnozzle.

WERNER ZARNACK;

References Cited in the file of this patent UNiTE'D STATES PA'I'ENT'S

